contains multiple words, flex fails.
Adjust tools/autoconf/Makefile to pass the necessary extra arguments via
M4=... in CONFIGURE_ENV. This is similar to what used to be in
revision 1.4 of tools/autoconf/Makefile, but it's now after instead of
before the inclusion of Makefile.gnuhost, because it has to override the
value of M4=... that Makefile.gnuhost stores in CONFIGURE_ENV.
in tools/Makefile.gnuhost. This makes the tools version of m4
behave like GNU m4.
Remove similar code from tools/autoconf/Makefile, where it didn't
work because Makefile.gnuhost would previously have overridden it.
This fixes a problem in which the tools version of autoconf complained
"M4sugar requires GNU M4.
Install it before installing M4sugar or set the M4 environment variable to its path name."
